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Title: Oxidation of iron-nitrosyl-hemoglobin by dehydroascorbic acid releases nitric oxide to form nitrite in human erythrocytes
Authors: Nathawut Sibmooh
Barbora Piknova
Fabiola Rizzatti
Alan N. Schechter
National Institute of Diabetes and Digestive and Kidney Diseases
Mahidol University
Keywords: Biochemistry, Genetics and Molecular Biology
Issue Date: 4-Mar-2008
Citation: Biochemistry. Vol.47, No.9 (2008), 2989-2996
Abstract: The reaction of deoxyhemoglobin with nitric oxide (NO) or nitrite ions (NO2-) produces ironnitrosyl-hemoglobin (HbNO) in contrast to the reaction with oxyhemoglobin, which produces methemoglobin and nitrate (NO3-). HbNO has not been associated with the known bioactivities of NO. We hypothesized that HbNO in erythrocytes could be an important source of bioactive NO/nitrite if its oxidation was coupled to the ascorbic acid (ASC) cycle. Studied by absorption and electron paramagnetic resonance (EPR) spectroscopy, DHA oxidized HbNO to methemoglobin and liberated NO from HbNO as determined by chemiluminescence. Both DHA and ascorbate free radical (AFR), the intermediate between ASC and DHA, enhanced NO oxidation to nitrite, but not nitrate; nor did either oxidize nitrite to nitrate. DHA increased the basal levels of nitrite in erythrocytes, while the reactions of nitrite with hemoglobin are slow. In erythrocytes loaded with HbNO, HbNO disappeared after DHA addition, and the AFR signal was detected by EPR. We suggest that the ASC-AFR-DHA cycle may be coupled to that of HbNO-nitrite and provide a mechanism for the endocrine transport of NO via hemoglobin within erythrocytes, resulting in the production of intracellular nitrite. Additionally, intracellular nitrite and nitrate seem to be largely generated by independent pathways within the erythrocyte. These data provide a physiologically robust mechanism for erythrocytic transport of NO bioactivity allowing for hormone-like properties.
ISSN: 00062960
Appears in Collections:Scopus 2006-2010

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